Router settings for BSNL

Hi,
I have been using airtel broadband plan for last few months. Now I have shifted to bsnl. my router is configured according to airtel settings.
Please help me to configure with bsnl as I am not able to connect to internet with bsnl.
my router is binatone DT845W

Thanks for replying
After following your instructions green light over the internet (in the router) started (initially it was off).
But now on trying to connect it is ERROR 651 (i.e. modem is NOT responding).
While i am able to access internet on reversing settings via airtel.
Please help

Thanks for trying to solve my problem.
You are absolutely right, I am using Windows 7.
I have tried both.
If I connect using dialer then it shows Error 651
and if I connect the other way (as you suggested) then it is showing DNS not responding.
The customer care of BSNL has NOT responded in last 5 days.
While talking on phone they seem to have NO idea of the problem and are saying that you have to change the modem.

Please deactivate all PVC Except PVC2 VPI/VCI 0 35.
Save each page.
(1a)
Presume you are trying to use BSNL and AIRTEL BB with SAME modem. For this model above procedure required every time you change the RJ11 input ( BSNL or Airtel )

(2)
Since you had used it for Airtel earlier only above page changes are required. ( Airtel page say PVC0 remains deactivated)

.
Download "Connectify" application and load in Laptop having
ethernet connection to Airtel or Bsnl.
(2.4)
This laptop will work as additional AP ( AccessPoint) within range.
Try later. as mentioned earrlier same wifi settings of Airtel will do for BSNL in the router.